It is a well-known fact that the surgical treatment of a deformed vertebra can be often complicated by a slight vertebral movement. For example, the deformation of a central rod of the vertebral fixation system is often brought about by the slight vertebral movement. For this reason, the conventional central rod fixation system for treating a deformed vertebra, such as the one disclosed in U.S. Pat. No. 5,387,212 by this inventor of the present invention, is provided with a longitudinal auxiliary fixation system which is intended to fix each of the horizontal fixing and retrieving members of the central rod fixation system.
Such a conventional central rod fixation system as described above is defective in design in that it is rather complicated in construction, and that its implementation can prolong the surgical duration, and further that it is unsuitable for use in a surgical treatment in which two bone screws must be fastened onto both sides of a vertebra at a rather short interval.